Percival was a member of the Knights of the Round Table, led by King Arthur, holding the 2nd Seat. He is often portrayed as the child of King Pellinore. He grew up in the forest and embarked on a quest for the Holy Grail alongside Sir Galahad and Sir Bors.
In Fate/Grand Order, Mordred makes a comment that Percival never wore a helmet.
Percival and the other Knights, apart from Bedivere and Galahad, are summoned by the Lion King. The Lion King tells them to choose to either help her with her "Holy Selection" or side against her, giving them a half a day to think. Percival politely talks with all other knights and then weeps alone afterward.
Percival ultimately sides against the Lion King, being killed in the following battle against his fellow knights.
Summoned as a Servant, Percival would be the "cream of the crop" when it comes to Heroic Spirits, like the other Knights of the Round Table. He could be summoned through the pieces of the Round Table.
According to Gawain in Fate/Grand Order, Percival had a knack when it came to cooking with root vegetables. Gawain was only second best after him.
During conversation in Fate/Extra CCC, Gawain mentions that when it came to chess he considered Percival and Galahad to be “worthy opponents”.
- ↑ Camelot/Zero translated at Beast's Lair
 Fate/Apocrypha material - Encyclopedia: Knights of the Round Table [Organization], p.156-157 [T]
Knights of the Round Table [Organization]
The general term for the knights who left their names in King Arthur’s legend. They are called the Knight of the Round Table because they gathered around a round table along with King Arthur. The knights sitting around the table were all regarded as equal to one another, including the King himself, and they were admired throughout the country. Though the number of them varies according to each story, the standard pattern of thirteen knights is accepted in “Fate/stay night”.
In the “Apocrypha” world, the separate splinters from the Round Table serve as summoning catalysts for Heroic Spirits. From among eleven of the knights (with King Arthur and Galahad excluded), the one most compatible to the Master is summoned through it. Like an S-rare definite ticket. Whether it be someone like Lancelot, Gawain, Tristan or Percival, no matter who comes, you truly get the cream of the crop. During these current times where subspecies Holy Grail Wars are popular, they appear in the market at high prices. Naturally, there are many frauds and swindlers. It’d be nice if a certain oil magnate got swindled.